Why not send an email to her instead of ____ (reply) to her letter?
如果AB>0,BC>0,那么直线Ax-By-C=0不经过的象限是 ( )
解方程组或解不等式组
(1)x+13-y+24=0x-34-y-33=112; (2)2x-13-5x+12≤15x-1<3x+1.